Single piece plastic bottle cap



I March 5, 1968 W. C. RUPRECHT SINGLE PIECE PLASTIC BOTTLE CAP FiledNov. 29, 1966 FIG. 1

w w w m ATTORNEYS Unite States Patent Ofiice 3,371,814 Patented Mar. 5,1968 3,371,814 SINGLE PIECE PLASTIC BOTTLE CAP Wallace C. Ruprecht,Mount Clemens, Mich, assignor to Ex-Cel Industries, Inc., Warren, Mich,a corporation of Michigan Filed Nov. 29, 1966, Ser. No. 597,672 9Claims. (Cl. 2115-40) This invention relates to an improved bottleclosure, such as the type used on soft drink or malt beverage bottles.More particularly, this invention relates to an improved single pieceplastic bottle cap, which provides a positive seal for conventionalbeverage bottles, even under relatively high pressures and temperatures.

Plastic bottle caps of the general type disclosed herein are known inthe art, however such devices have not been commercially successful,because of inherent limitations or defects in their design, which makethem unacceptable to commercial bottlers. One failure of previousplastic bottle caps is their inherent inability to seal bottles in theaccepted range of bottle manufacturers dimensional tolerances. Another,is their high initial cost, and lack of adaptability to conventionalcrowning or capping operations. Further, previous bottle cap designsgenerally do not provide a positive seal under the relatively hightemperature and pressure conditions present in the bottling of maltbeverages.

One group of prior art plastic bottle caps provides an annular lip, orother sealing means, which extends into the bottle opening to sealagainst the internal bottle wall. This group includes the followingpatents: 2,699,369, 2,820,563, 2,914,206, 2,953,272, 2,987,206,2,991,902, 3,038,624, 3,069,040, 1,107,541, Germany (allowedapplication) May 1961. The inside diameter, however, of conventionalbeverage bottles, may vary from 0.040 to 0.060 inch, which make suchclosures unacceptable without bottle redesign, because the sealing meansis intended to seal against the inside diameter of the bottle.Conversely, the external diameter of the annular bottle rib, which isgripped by the more conventional metal cap, is held within 0.005 inch.Further, such closures do not adequately seal under pressure.

Another group of plastic closures, shown by the prior art, reliesprimarily on one or more sealing lips which engage the external topportion of the bottle. Such caps are typically threaded to the bottleneck, because the sealing means must be continuously urged against thebottle top to maintain sealing engagement. An air gap is generallyprovided between the top of the bottle and the cap, on the theory thatthe pressure within the bottle will urge the lip into the sealingposition. Examples of this group of closures are as follows: 3,053,406,3,067,900, 3,151,757, 3,160,303, 202,476, Austrian, Mar. 1959,1,213,812, French, Nov. 1959.

Such designs are unacceptable for the more conventional snap-on beveragebottles which have an annular rib on the bottle neck adjacent theopening, and have not been commercially accepted even in threadedcontainers, where pressure within the container varies with temperature.Such closures are also relatively expensive to manufacture, because ofthe complexity of their design.

A final group of plastic closures will be discussed herein, involves anattempt to retain the basic configuration of the conventional two-piecemetal bottle cap, by providing a plastic sealing disc, which sealinglyengages the bottle top, and is positioned within the cap. Such bottlecap designs have little advantage over the more conventional metalbottle cap, and generally do not seal as Well as the metal cap, becausethe plastic skirt portion cannot be crimped over the external annularbottle rib. An example of this type of closure is United States PatentNo. 2,906,421.

A suitable replacement for the conventional metal bottle cap has longbeen sought by the bottling industry, as evidenced by the above-listedreferences. The two part metal bottle cap is relatively expensive toproduce, requires crimping of the skirt portion against the bottle inthe crowning operation, and may permit deterioration of the containedbeverage on extended storage. The metal cap has a separate cork sealinsert, which will shrink as it dries, permitting leakage around thecork seal. Further, the metal cap is rigid, and therefore cannot yieldto permit pressure relief, without leakage.

An object of the closure of this invention is to provide a single pieceplastic bottle closure, which will seal conventional beverage bottles inthe range of bottle manufacturers dimensional tolerances.

Another object of this invention is to provide a closure for soft drinkand malt beverage bottles which will not be affected by changes intemperature or pressure.

An object of this invention is to provide a plastic bottle cap which caneasily be adapted to conventional crownmg processes.

Another object of this invention is to provide a plastic bottle closurewhich is less expensive than conventional metal bottle caps, and whichis not subject to leakage or deterioration of the seal.

A further object of this invention is to provide a bottle cap which iscapable of relieving pressure within the bottle, without leakage orbottle fracture.

Another object of this invention is to provide a plastic closure whichmay easily be removed, without sacrificing the sealing capability of theclosure.

The bottle cap of this invention has internal annular groove, defined inthe skirt portion, which closely overlies and substantially conforms tothe annular rib of the conventional beverage bottle, adjacent the bottleopening. A thin annular sealing lip is joined to the skirt portion,Within the annular groove, which has a downwardly and inwardly extendingportion. The annular lip is reversely biased over theupper portion ofthe annular bottle rib, during the crowning operation, which stretchesthe lip to closely conform to the annular rib. Considerable forces areset up in the annular lip, which maintains the lip in sealing relation.These forces may be characterized as hoop stress or hoop tension, andprovides a perfect seal between the lip portion and the bottle top,without the necessity of an air gap therebetween. The integral topportion of the plastic bottle cap of this invention may be a thinelastic membrane, which is capable of yielding to relieve pressurewithin the bottle, without leakage or fracture of the bottle.

According to one embodiment of the bottle cap of this invention, theskirt portion is provided with a radially outwardly extending integraltab, and the skirt portion has been weakened, adjacent the joinder ofthe tab and the skirt portion, to yield on upward urging of the tab.This closure may thus be easily removed without sacrificing the sealingpotential of the basic closure design.

Other objects, advantages, and meritorious features will more fullyappear from the following specification, claims, and accompanyingdrawings, wherein:

FIGURE '1 is a top view of one embodiment of the closure of thisinvention;

FIGURE 2 is a side cross-sectional view of the closure shown in FIGURE1;

FIGURE 3 is a side cross-sectional view of the closure shown in FIGURES1 and 2, received on a bottle;

FIGURE 4 is a view, similar to FIGURE 3, illustrating the effect ofincreased internal bottle pressure;

FIGURE 5 is a side cross-sectional view of the closure embodiment ofFIGURES l to 4, after the closure is removed from the bottle;

FIGURE 6 is a top view of another embodiment of the closure of thisinvention; and

FIGURE 7 is a side cross-sectional view of the closure embodiment shownin FIGURE 6, in the direction of view arrows 77.

FIGURES 1 to illustrate one embodiment of the plastic closure 20, ofthis invention. The closure has a top portion 22, which overlies theopening 24 of the bottle 30. and an integral skirt portion 26, whichextends from the top portion of the closure to overlie the externalannular rib 28 of the bottle. The neck portion of the bottle 32.illustrated in FIGURES 3 and 4, is conventional in soft drink and maltbeverage bottles. The annular rib 28, which is gripped by theconventional metal bottle cap, is held within 0.005 inch on the diameterto assure scaling in the crowning operation.

An annular groove 34 is defined in the skirt portion, which closelyoverlies, and substantially conforms to the external annular rib 28 ofthe bottle. An inwardly extending thin conical lip 36 is joined to theskirt portion, within the annular groove, to provide a positive sealadjacent the bottle opening 24. Prior to the crowning or cappingoperation, the lip extends generally downwardly and inwardly, as shownin FIGURE 2.

During the crowning operation, i.e. as the cap is mounted on the bottlemouth, the lip is reversely biased and stretched over the upper portionof the annular bottle rib 28, as shown in FIGURES 3 and 4, to assume aconcave-convex cross-sectional shape. The reverse biasing of the annularlip 36, over the bottle rib 28, produces considerable forces in the lip,which are directed inwardly, toward the axis of the annular lip, andcause the lip to closely conform to the upper portion of the annularbottle rib. These forces may be characterized as hoop stress, or hooptension, as they are the resultant axially directed forces in a hoop orannulas as it is stretched away from its axis. The forces set up in theannular lip, during the crowning operation, are sufiicient to maintainan extremely tight seal, without the necessity of crimping the skirtportion over the annular rib, as is required with conventional metalcaps. The lip also serves to aid in the retention of the closure on thebottle top, much as a shrink fitted metal ring is retained on a shaft.The ring is retained by hoop stress, directed toward the axis of theshaft.

It can be seen from FIGURES 3 and 4, that the top portion 22 of theclosure is slightly biased over the annular lip 36, which eliminatesformation of an air gap, which is characteristic of many prior artbottle closures. Further, the lower portion of the skirt 38, defines aninternal annular rib, which is received beneath the external annular rib24 of the bottle, to prevent upward motion of the closure under pressurewithin the bottle, acting against the underside of the top portion.

The top portion 22, of this embodiment of the plastic closure, may becharacterized as an elastic membrane, capable of compensating forchanges in pressure within the bottle, without sacrificing the sealingpotential of the closure. It can be seen from FIGURE 4, that the top ofthe closure will yield to assume a concave or convex configuration,without affecting the seal provided by the annular lip 36. The seal isindependent of this portion of the closure top, and therefore the sealwill be substantially independent of changes in pressure andtemperature.

FIGURE 5 illustrates the condition of the annular lip 36, after theclosure has been removed from the bottle, and the forces exerted on thelip during the crowning operation.

The location of the lip, within the annular groove 34, is an importantfeature to the sealing potential of the closure of this invention. Asdescribed hereinabove, the annular lip cooperates with the annularbottle rib 28 and the annular groove 34, to seal the bottle opening.This cooperation will be affected by the location of the joinder of theannular lip to the skirt portion 40. In the embodiment of the closureshown in the drawings, the lip is joined to the skirt portionsubstantially at the center of the annular groove 34, which generallycoincides with the mid portion of the annular bottle rib 28. Thisrelationship has been found to provide an excellent seal, however thecritical relationship is that the lip is joined to the skirt portion,within the annular groove, below the top of the annular bottle rib, toprovide the stress relationship described hereinabove.

The plastic closure of this invention is particularly adapted toconventional crowning techniques used by commercial bottlers, andcommercial crowners. In a commercial crowner, the metal bottle caps aredelivered to a rotating crowner head from a hopper. Bottles aredelivered, on a conveyor, beneath the crowner head, which retains aplurality of caps parallel to the bottle tops. The moving bottles arebrought into contact with the caps, and the skirt portions are crimped,beneath the annular bottle rib, by a reciprocating piston. The crimpingoperation may cause fracture of the bottles, requiring shutdown of theline, and adjustment of the head.

The closure of this invention may be secured in a similar manner,utilizing a commercial crowner, however the crimping operation has beeneliminated. The closures are retained in the rotating crowner head,parallel to the top of the moving bottles, and seated as the bottles arelifted into the crowner head. The elimination of the crimping operationreduces the maintenance on the crowner, and eliminates fracture of thebottles during the crimping operation.

FIGURES 6 and 7 illustrate another embodiment of the plastic closure ofthis invention, which is designed to be easily removed from a bottle.The basic features of the closure are similar to the closure describedhereinabove in reference to FIGURES l to 5, and have been numberedaccordingly.

The closure of this embodiment is provided with a radially outwardlyextending tab 142, and the skirt portion 126 has been weakened adjacentthe joinder of the tab and the skirt portion, at 144, on opposite sidesof the tab. The closure may be removed by urging the tab upward, whichcauses the skirt portion to yield at the weakened areas 144.

The weakened areas of the skirt 144, may extend through the joinder ofthe lip and the skirt portion 140, to break the seal as the tab is urgedupwardly. The tab may also be provided with structural reinforcements,as required, such as the reinforcing ribs 146, shown in FIG- URE 6.

The lip 136, of this embodiment of my closure, has been joined to theskirt portion 126 slightly below the center of the annular groove 134.The lip portion will be stretched over the annular bottle rib below theaxis of the rib. This will increase the hoop tension as the lip isreversely biased over the bottle rib, in the crowning operation.

Any of various materials may be used for the closure of this invention,however polyethylene, especially linear polyethylene, has proven to besatisfactory. Linear polyethylene is tasteless, and may be injectionmolded. Further, linear polyethylene provides the structuralcharacteristics required for the features disclosed hereinabove.

What is claimed is:

1. A bottle closure for sealing the opening of a bottle having anexternal annular rib adjacent the top of the bottle neck portion,comprising: an annular skirt portion adapted to overlie an annular ribof the bottle neck, and an integral top portion adapted to overlie thebottle opening, said skirt portion having an internal annular groovewhich closely overlies and substantially conforms to the externalannular rib of the bottle, and an inwardly extending thin conical lipjoined to said skirt portion within said annular groove adapted to bereversely biased over the upper portion of the external annular rib ofthe bottle in stressed relation to seal the bottle opening when saidskirt portion is seated over the annular rib of the bottle.

2. The bottle closure defined in claim 1, characterized in that saidconical lip is adapted to closely conform to the internal annular grooveof said skirt portion and the upper portion of the annular rib of thebottle in the biased condition, to prevent formation of an air gapbetween said skirt portion and the bottle top.

3. The bottle closure defined in claim 1, characterized in that saidthin conical lip is joined to said skirt portion generally at the centerat said annular groove.

4. The bottle closure defined in claim 1, characterized in that saidinwardly extending thin conical lip extends downwardly at an acute angleto the axis of the closure.

5. The bottle closure defined in claim 1, characterized in that said topportion is a thin elastic sheet adapted to relieve pressures Within thebottle.

6. The bottle closure defined in claim 1, characterized in that saidskirt portion terminates in an elastic rib which is received beneath theannular rib of the bottle neck to inhibit removal of the cap from thebottle top.

7. The bottle closure defined in claim 1, characterized in that saidskirt portion includes a radially outwardly projecting tab portion andsaid skirt portion includes weakened areas adjacent the joinder of saidtab and said skirt 6 portion to aid in the removal of the bottle cap bylifting said tab.

8. In combination, a bottle having a neck portion including a centralopening and an adjacent external annular rib, and a single piece plasticclosure having a skirt portion overlying said annular rib and a topportion overlying said bottle opening, said skirt portion having aninternal annular groove closely overlying and substantially conformingto said annular bottle rib and a thin annular lip joined to said skirtportion within said annular groove, said annular lip stretched over theupper portion of said annular bottle rib and conforming to said annularrib and said annular groove Without formation of an air gap between saidclosure top portion and the bottle top openmg.

9. The invention defined in claim 8, characterized in that said thinannular lip is joined to said skirt portion Within said annular groovebelow the top of said annular bottle rib.

References Cited FOREIGN PATENTS 4/1952 France. 6/1960 France.

8. IN COMBINATION, A BOTTLE HAVING A NECK PORTION INCLUDING A CENTRALOPENING AND AN ADJACENT EXTERNAL ANNULAR RIB, AND A SINGLE PIECE PLASTICCLOSURE HAVING A SKIRT PORTION OVERLYING SAID ANNULAR RIB AND A TOPPORTION OVERLYING SAID BOTTLE OPENING, SAID SKIRT PORTION HAVING ANINTERNAL ANNULAR GROOVE CLOSELY OVERLYING AND SUBSTANTIALLY CONFORMINGTO SAID ANNULAR BOTTLE RIB AND A THIN ANNULAR LIP JOINED TO SAID SKIRTPORTION WITHIN SAID ANNULAR GROOVE, SAID ANNULAR LIP STRETCHED OVER THEUPPER PORTION OF SAID ANNULAR BOTTLE RIB AND CONFORMING TO SAID ANNULARRIB AND SAID ANNULAR GROOVE WITHOUT FORMATION OF AN AIR GAP BETWEEN SAIDCLOSURE TOP PORTION AND THE BOTTLE TOP OPENING.